Exposure pattern forming method and exposure pattern

ABSTRACT

The present invention provides an exposure pattern forming method using a rule-based proximity effect correction method to which graphic form arithmetic operation is applied.  
     Disclosed is an exposure pattern forming method of forming an exposure pattern by correcting each of pattern portions constituting a design pattern by a correction amount, which amount is previously prepared so as to correspond to both a line width of the pattern portion and a space width of a space portion adjacent to the pattern portion, characterized by including the steps of: subjecting the design pattern to graphic form arithmetic operation, to extract each of the pattern portions for each of target line widths, and to extract each of the space portions for each of target space widths (ST 2,  ST 3 ); and subjecting each of the pattern portion extracted for each of the target line widths and the space portion extracted for each of the target space widths to graphic form arithmetic operation based on the corresponding one of the correction amounts, to thereby correct the pattern portion having each of the target line widths for each of the target space widths (ST 4  to ST 9 ).

TECHNICAL FIELD

The present invention relates to an exposure pattern forming method andan exposure pattern formed by the method, and particularly to anexposure pattern forming method to which a rule-based proximity effectcorrection method is applied and an exposure pattern formed by themethod.

BACKGROUND ART

In fabrication of semiconductor devices, resist patterns are used asmasks for ion implantation and pattern etching.

With respect to such resist patterns obtained by photolithography andtransfer patterns formed from the resist patterns by etching, it isknown that variations in dimensional accuracy may occur due to variousfactors such as process conditions, arrangement densities of thepatterns, and underlying conditions. Such variations in dimensionalaccuracy may cause defects such as short-circuit between the patternsand disconnection of the patterns.

In recent years, an attempt has been made to obtain transfer patternscloser to design patterns by correcting designed pattern in accordancewith a so-called optical proximity effect correction (hereinafter,referred to as “OPC”) method. One type of the OPC method is known as arule-based OPC, wherein a correction amount corresponding to both a linewidth of each pattern portion of a design pattern and a space width of aspace portion adjacent to the pattern portion is extracted by searchinga previously prepared correction table, and the pattern portion iscorrected by the correction amount thus extracted.

One specific method of extracting a correction amount corresponding toeach pattern portion of a design pattern by using the rule-based OPCmethod is known as that using a DRC (Design Rule Checker). In the methodusing the DRC, each pattern having a target line width or each spaceportion having a target space width is extracted by setting a flag at anedge of a design pattern, depicting a circle having a radius equivalentto a target distance (target line width or target space width) aroundthe flag, and sampling a portion with its edge portion contained in thecircle as a target pattern portion or a target space portion. Eachpattern portion of the design pattern is then corrected by a correctionamount corresponding to both the sampled pattern portion and the spaceportion.

The method of extracting the target pattern portion and the target linewidth portion using the DRC, however, has the following problem.Referring to FIG. 14, at a portion between two pattern portions 101, inwhich the space width is changed between target space widths S1 and S2,according to the method using the DRC, a calculated edge portion, whichis extracted as that having the target space width S1, is protrudedoutwardly from an actual edge portion. Accordingly, the portion in whichthe space width is changed between the values S1 and S2 cannot beaccurately corrected. In other words, there may occur a partialdeviation between the correction amount given to the above portion and acorrection amount required for the portion.

In the case of forming a transfer pattern on a substrate byphotolithography using an exposure pattern corrected on the basis of theabove-described erroneous extraction, there may occur a defect such asshort-circuit or disconnection of the transfer pattern at theabove-described portion partially deviated from the design pattern. Upuntil now, it has failed to certainly solve the above-described problemof the method using the DRC.

In view of the foregoing, an object of the present invention is toprovide an exposure pattern forming method capable of forming anexposure pattern by accurately correcting a design pattern, and toprovide an exposure pattern formed by the method.

DISCLOSURE OF INVENTION

To achieve the above object, according to the present invention, thereis provided an exposure pattern forming method of forming an exposurepattern by correcting each of pattern portions constituting a designpattern by a correction amount, which amount is previously prepared soas to correspond to both a line width of the pattern portion and a spacewidth of a space portion adjacent to the pattern portion, characterizedby including the steps of: subjecting the design pattern to graphic formarithmetic operation, to extract each of the pattern portions for eachof target line widths, and to extract each of the space portions foreach of target space widths; and subjecting each of the pattern portionextracted for each of the target line widths and the space portionextracted for each of the target space widths to graphic form arithmeticoperation based on the corresponding one of the correction amounts, tothereby correct the pattern portion having each of the target linewidths for each of the target space widths. The present invention alsoprovides an exposure pattern formed by the method.

According to the exposure pattern forming method and the exposurepattern, a pattern portion having each of target line widths and a spaceportion having each of target space widths are extracted by graphic formarithmetic operation. Accordingly, a pattern portion having a targetdimension and a space portion having a target dimension can beaccurately extracted irrespective of the arrangement states of thepattern portion and the space portion. Each of the extracted portions isthen subjected to graphic form arithmetic operation based on thecorresponding correction amount, to thus correct the design pattern. Asa result, since the design pattern is corrected only by graphic formarithmetic operation without use of any special measurement method, anypattern portion can be corrected irrespective of the shape of the designpattern.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow chart illustrating a pattern forming method of thepresent invention;

FIGS. 2A and 2B are views showing a procedure of obtaining a minusdifferential graphic form between a design pattern and a correctionpattern obtained by correcting the design pattern by each minuscorrection amount in accordance with the pattern forming method of thepresent invention;

FIGS. 3A and 3B are views showing a procedure of obtaining a plusdifferential graphic form between a design pattern and a correctionpattern obtained by correcting the design pattern by each pluscorrection amount in accordance with the pattern forming method of thepresent invention;

FIGS. 4A to 4D are views (part 1) illustrating a procedure of extractinga pattern portion having each target line width in accordance with thepattern forming method of the present invention;

FIGS. 5A to 5E are views (part 2) illustrating a procedure of extractinga pattern portion having each target line width in accordance with thepattern forming method of the present invention;

FIGS. 6A to 6D are views (part 1) illustrating a procedure of extractinga space portion having each target space width in accordance with thepattern forming method of the present invention;

FIGS. 7A to 7E are views (part 2) illustrating a procedure of extractinga space portion having each target space width in accordance with thepattern forming method of the present invention;

FIGS. 8A to 8E are views (part 1) illustrating a procedure of obtaininga plus bias correction graphic form in accordance with the patternforming method of the present invention;

FIGS. 9A to 9E are views (part 2) illustrating a procedure of obtaininga minus bias correction graphic form in accordance with the patternforming method of the present invention;

FIGS. 10A to 10E are views (part 1) illustrating a procedure ofobtaining a plus bias correction graphic form of a pattern portionadjacent to a space portion having an infinite space width in accordancewith the pattern forming method of the present invention;

FIGS. 11A to 11F are views (part 2) illustrating a procedure ofobtaining a minus bias correction graphic form of a pattern portionadjacent to a space portion having an infinite space width in accordancewith the pattern forming method of the present invention;

FIGS. 12A to 12C are views illustrating a procedure of correcting amicro-recess after bias correction in accordance with the patternforming method of the present invention;

FIGS. 13A to 13C are views illustrating a procedure of correcting amicro-projection after bias correction in accordance with the patternforming method of the present invention; and

FIG. 14 is a view illustrating a problem of a related art method.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be hereinafter describedwith reference to the drawings.

In this embodiment, the present invention is applied to a rule-based OPCmethod including the steps of extracting a correction amount “d”corresponding to both a line width L (L1 to L7) of each of patternportions constituting a design pattern and a space width S (S1 to S10)of a space portion adjacent to an edge of the pattern portion bysearching previously prepared correction data shown in Table 1, andcorrecting an edge of a pattern portion of the design pattern by thecorresponding correction amount. TABLE 1 L\S S1 ≦ a1 a1 < S2 ≦ a2 . . .ax < Sy ≦ ay ay < Sz L1 ≦ b1 d11 d12 . . . d1y d1z b1 < L2 ≦ d21 * d22 . . . d2y d2z b2 . . . d31 . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . bx < Ly ≦ dy1 dy2 . . . dyy dyz by by < Lz dz1 dz2 . . .dzy dzz

In Table 1, for example, a value d22 in the middle column given a symbol“*” means that a correction amount “d” of an edge portion, adjacent to aspace portion having a space width S2 in a range of a1<S2≧a2, of apattern portion having a line width L2 in a range of b1<L2≦b2 is d22.

FIG. 1 is a flow chart showing an exposure pattern forming methodaccording to the present invention. A procedure of forming an exposurepattern by correcting a design pattern will be described below in theorder of procedures shown in the flow chart with reference to FIG. 1 andTable 1, and if needed, other figures.

[First Step ST1]

In the first step ST1, a design pattern (before correction) is correctedby each correction amount “d” shown in Table 1, to obtain a correctionpattern, and a differential graphic form between the design pattern andthe correction pattern is extracted. For example, as shown in FIG. 2A,for a correction amount d=−10 nm, an edge portion of a design pattern 1is subjected to reduction correction (undersize correction) in which theedge portion is shifted by an amount of 10 nm in the undersizedirection, to prepare a correction pattern 3, and as shown in FIG. 2B, aminus differential graphic form 5 is obtained by subtracting thecorrection pattern 3 from the design pattern 1.

As shown in FIG. 3A, for a correction amount d=+10 nm, the edge portionof the design pattern 1 is subjected to enlargement correction (oversizecorrection) in which the edge portion is shifted by an amount of 10 nmin the oversize direction, to prepare a correction pattern 3, and asshown in FIG. 3B, a plus differential graphic form 5′ is obtained bysubtracting the design pattern 1 from the correction pattern 3.

The above preparation of the set of the differential graphic forms 5 and5′ is repeated for each of the other correction amounts “d” shown inTable 1. If six kinds of the correction amounts “d” are listed in Table1, six sets of the differential graphic forms 5 and 5′ are prepared. Itis to be noted that the sets of the differential graphic forms 5 and 5′are to be used for the subsequent graphic form arithmetic operation forcorrection.

[Second Step ST2]

In the second step ST2, a design pattern is subjected to graphic formarithmetic operation for each of target line widths L of patternportions constituting the design pattern, to extract each patternportion as that having the target line width L. Here, since each of thetarget line widths L1, L2, . . . is set to be in a specific range asshown in Table 1, as will be described below, the design pattern issubjected to graphic form arithmetic operation for each target linewidth in the corresponding specific range, to extract each patternportion as that having the target line width in the correspondingspecific range.

A design pattern 1 shown in FIG. 4A is under-sized by a correctionamount equivalent to ½ of an upper limit value (b1) of a range (L1≦b1)of a minimum level line width L1, to obtain an undersized graphic formshown in FIG. 4B, and the undersized graphic form shown in FIG. 4B isover-sized by the same correction amount, to obtain a correction pattern7 shown in FIG. 4C. The correction pattern 7 is then subtracted from thedesign pattern 1, to extract a graphic form as a pattern portion 1L₁having the line width L1 in the range of L1≦b1 as shown in FIG. 4D.

The design pattern 1 shown in FIG. 5A is also under-sized by acorrection amount equivalent to 1/2 of an upper limit value (b2) of arange (b1<L2≦b2) of a next level line width L2, to obtain an undersizedgraphic form shown in FIG. 5B, and the undersized graphic form shown inFIG. 5B is over-sized by the same correction amount, to obtain acorrection pattern 7′ shown in FIG. 5C. The correction pattern 7′ isthen subtracted from the design pattern 1, to obtain a graphic formshown in FIG. 5D. The above pattern portion 1L₁ in the range of L1≦b1 isthen subtracted from the graphic form shown in FIG. 5D, to extract agraphic form as a pattern portion 1L₂ having the line width L2 in therange of b1<L2≦b2 as shown in FIG. 5E.

The above-described extraction of the pattern portion is repeated, tothus extract the pattern portions 1L₁, 1L₂, . . . , 1L_(z) having thetarget line widths L1, L2, . . . , Lz, respectively. In this case, theextraction of the pattern portions is performed in the order from thesmaller value of the line width L to the larger value of the line widthL.

The extraction of the pattern portions 1L₁, 1L₂, . . . , 1L_(z) may beperformed by extracting the correction pattern 7 shown in FIG. 4C as apattern portion having a line width larger than b1 and extracting thecorrection pattern 7′ shown in FIG. 5C as a pattern portion having aline width larger than b2. In this case, the extraction of the patternportions is performed in the order from the larger value of the linewidth L to the smaller value of the line width L.

To be more specific, the design pattern 1 is under-sized by a correctionamount equivalent to ½ of a value “by” and the undersized graphic formis over-sized by the same correction amount, and the resultant graphicform is subtracted from the design pattern 1, to extract a graphic formas a pattern portion having a line width larger the value “by”, that is,a pattern portion 1L_(y) having the line width Ly in the range of by<Ly.The design pattern 1 is also under-sized by a correction amountequivalent to ½ of a value (bx) and the undersized graphic form isover-sized by the same correction amount, and the resultant graphic formis subtracted from the design pattern 1, to obtain a graphic form as apattern portion having the line width larger than bx. The above patternportion 1L_(y) in the range of by<Ly is then subtracted from the abovepattern portion having the line width larger than bx, to extract agraphic form as a pattern portion 1L_(x) having the line width Lx in therange of bx<Lx≦by. In this way, the extraction of the pattern portionsis performed in the order from the larger value of the line width L tothe smaller value of the line width L.

[Third Step ST3]

In the third step ST3, a design pattern is subjected to graphic formarithmetic operation for each of target space widths S of space portionsaround the design pattern, to extract each space portion as that havingthe target space width S. Here, since each of the target space widthsS1, S2, . . . is set to be in a specific range as shown in Table 1, aswill be described below, the design pattern is subjected to graphic formarithmetic operation for each target space width in the correspondingspecific range, to extract each space portion as that having the targetspace width in the corresponding specific range.

A design pattern 1 shown in FIG. 6A is over-sized by a correction amountequivalent to ½ of an upper limit value (a1) of a range (S1≦a1) of aminimum level space width S1, to obtain an oversized graphic form shownin FIG. 6B, and the oversized graphic form shown in FIG. 6B isunder-sized by the same correction amount, to obtain a correctionpattern 9 shown in FIG. 6C. The design pattern 1 is then subtracted fromthe correction pattern 9, to extract a graphic form as a pattern portion1S₁ having the space width S1 in the range of S1≦a2 as shown in FIG. 6D.

The design pattern 1 shown in FIG. 7A is also over-sized by a correctionamount equivalent to ½ of an upper limit value (a2) of a range(a1<S2≦a2) of a next level space width S2, to obtain an oversizedgraphic form shown in FIG. 7B, and the oversized graphic form shown inFIG. 7B is under-sized by the same correction amount, to obtain acorrection pattern 9′ shown in FIG. 7C. The design pattern 1 is thensubtracted from the correction pattern 9′, to obtain a graphic formshown in FIG. 7D and the above pattern portion 1S₁ in the range of S1≦a1is subtracted from the graphic form shown in FIG. 7D, to extract agraphic form as a space portion 1S₂ having the space width S2 in therange of a1<S2≦a2 as shown in FIG. 7E.

The above-described extraction of the space portion is repeated, to thusextract the space portions 1S₁, 1S₂, . . . , 1S_(z) having the targetline widths S1, S2, . . . , Sz, respectively. In this case, theextraction of the space portions is performed in the order from thesmaller value of the space width S to the larger value of the spacewidth S.

In each of the first, second, and third steps ST1, ST2, and ST3, theextracting order is not limited to that described above but may befreely changed.

[Fourth Step ST4]

In the fourth step ST4, to correct each pattern portion of the designpattern, the pattern portion is combined with a space portion adjacentto each of edges of the pattern portion.

[Fifth Step ST5]

In the fifth step ST5, it is decided whether or not a space portionadjacent to each of all the edges of each pattern portion is infinite.It is to be noted that as shown in Table 1, a space width Sz, which islarger than ay, is taken as being infinite. If the answer in the fifthstep ST5 is negative (No), that is, if it is decided that a spaceportion adjacent to each of all the edges of each pattern portion is notinfinite, the process goes on to a sixth step ST6. If the answer in thefifth step ST5 is affirmative (Yes), that is, if it is decided that aspace portion adjacent to all the edges of each pattern portion isinfinite, the process goes on to a seventh step ST7.

[Sixth Step ST6]

In the sixth step ST6, an edge portion adjacent to a space portionhaving a space width decided not to be infinite, that is, having a spacewidth in the range of the space width S1 to the space width Sz(exclusive) shown in Table 1 is taken as that to be corrected, and it isdecided whether or not the correction amount “d” of the edge portion tobe corrected is positive (+), negative (−), or zero (0). If it isdecided that the correction amount is positive (+), the process goes onto an eighth step ST8 via a sub-step ST6 a, and if it is decided thatthe correction amount is negative (−), the process goes on to the eighthstep ST8 via a sub-step ST6 b. Meanwhile, if it is decided that thecorrection amount is zero (0), the process directly goes on to theeighth step ST8.

[Sub-Step ST6 a]

A plus bias operation performed when it is decided that the correctionamount “d” is positive (+) in the sixth step ST6 will be described byexample of a pattern portion having the line width L2 and the spacewidth S2 of Table 1.

Each of all the pattern portions 1L₂ extracted as those each having theline width L2, which is shown in FIG. 8A, is over-sized by a correctionamount d=d22 (for example, +10 nm) corresponding to both the line widthL2 and the space width S2, to obtain a correction graphic form 11 shownin FIG. 8B. As shown in FIG. 8C, the plus differential graphic form 5′corresponding to the correction amount d=d22 obtained in the first stepST1 and the correction graphic form 11 are subjected to AND operation,to obtain an AND graphic form 13. As shown in FIG. 8D, the space portion1S₂ extracted as that having the target space width S2 in the third stepST3 and the AND graphic form 13 shown in FIG. 8C are subjected to ANDoperation, to obtain an AND graphic form shown in FIG. 8E, which istaken as a plus bias graphic form 15.

The plus bias operation shown in FIGS. 8A to 8E is repeated for each ofthose, the correction amount of which is decided as positive (+) in thesixth step ST6, of all the edge portions each having the space width inthe range from the space width S1 to the space width Sy (inclusive), toobtain the corresponding plus bias graphic forms 15.

[Sub-Step ST6 b]

A minus bias operation performed when it is decided that the correctionamount is negative (1) in the sixth step ST6 will be described by way ofan example in which it is assumed that in Table 1, a correction amountdy2 corresponding to an edge portion having a line width Ly and a spacewidth S2 is negative.

Each of all the pattern portions 1S₂ extracted as those each having thespace width S2, which is shown in FIG. 9A, is over-sized by a correctionamount d=dy2 (for example, −10 nm) corresponding to both the line widthLy and the space width S2, to obtain a correction graphic form 21 shownin FIG. 9B. As shown in FIG. 9C, the minus differential graphic form 5corresponding to the correction amount (−10 nm) obtained in the firststep ST1 and the correction graphic form 21 are subjected to ANDoperation, to obtain an AND graphic form 23. As shown in FIG. 9D, thepattern portion 1L_(y) extracted as that having the target space widthLy in the third step ST3 and the AND graphic form 23 shown in FIG. 9Care subjected to AND operation, to obtain an AND graphic form shown inFIG. 9E, which is taken as a minus bias graphic form 25.

The minus bias operation shown in FIGS. 9A to 9E is repeated for each ofthose, the correction amount of which is decided as negative (−) in thesixth step ST6, of all the edge portions each having the space width inthe range from the space width S1 to the space width Sy (inclusive), toobtain the corresponding minus bias graphic forms.

[Seventh Step ST7]

In the seventh step ST7, it is decided whether or not a correctionamount of each edge portion adjacent to a space portion having aninfinite space width (Sz) is positive (+), negative (−), or zero (0). Ifit is decided that the correction amount is positive (+), the processgoes on to the eighth step ST8 via a sub-step ST7 a, and if it isdecided that the correction amount is negative (−), the process goes onto the eighth step ST8 via a sub-step ST7 b. Meanwhile, if it is decidedthat the correction amount is zero (0), the process directly goes on tothe eighth step ST8.

[Sub-Step ST7 a]

A plus bias operation performed when it is decided that the correctionamount is positive (+) in the seventh step ST7 will be described by wayof an example in which it is assumed that in Table 1, a correctionamount d2 z of a target edge portion having the line width L2 and thespace width Sz is positive.

Each of all the pattern portions 1L₂ extracted as those each having theline width L2, which is shown in FIG. 10A, is over-sized by a correctionamount d=d2 z (for example, +10 nm) corresponding to both the line widthL2 and the space width Sz, to obtain a correction graphic form 31 shownin FIG. 10B. As shown in FIG. 10C, the plus differential graphic form 5′corresponding to the correction amount d=d2 z obtained in the first stepST1 and the correction graphic form 31 are subjected to AND operation,to obtain an AND graphic form 33. Space portions 1S₁ to 1S_(y) otherthan the space portion having the space width Sz are extracted as shownin FIG. 10D, and as shown in FIG. 10E, the space portions 1A₁ to 1S_(y)are subtracted from the AND graphic form 33, to obtain a plus biasgraphic form 35.

The plus bias operation shown in FIGS. 10A to 10E is repeated for eachof those, the correction amount of which is decided as positive (+) inthe seventh step ST7, of all the edge portions having the space widthSz, to obtain the corresponding plus bias graphic forms 35.

[Sub-Step ST7 b]

A minus bias operation performed when it is decided that the correctionamount “d” is negative (−) in the seventh step ST7 will be described byway of an example in which it is assumed that in Table 1, a correctionamount dyz corresponding to an edge portion having a line width Ly and aspace width Sz is negative.

Each of all the space portions 1S₁ to 1S_(y) other than the spaceportion having the space width Sz, which is shown in FIG. 11A, isover-sized by an absolute value of a correction amount d=dyz (forexample, −10 nm) corresponding to both the line width Ly and the spacewidth Sz, to obtain a correction graphic form 41 shown in FIG. 11B. Asshown in FIG. 11C, the minus differential graphic form 5 correspondingto the correction amount d=−10 nm obtained in the first step ST1 and thecorrection graphic form 41 are subjected to AND operation, to obtain anAND graphic form 43. The pattern portion 1L_(y) extracted as that havingthe target space width Ly in the third step ST3, which is shown in FIG.11D, and the minus differential graphic form 5 corresponding to thecorrection amount d=−10 nm obtained in the first step ST1 are subjectedto AND operation, to obtain an AND graphic form 45 shown in FIG. 11E.The AND graphic form 43 shown in FIG. 11C is subtracted from the ANDgraphic form 45, to obtain a graphic form shown in FIG. 11F, which istaken as a minus bias graphic form 47.

The minus bias operation shown in FIGS. 11A to 11F is repeated for eachof those, the correction amount of which is decided as negative (−) inthe seventh step ST7, of all the edge portions each having the spacewidths Sz, to obtain the corresponding minus bias graphic forms 47.

[Eighth Step ST8]

All of the plus bias graphic forms 15 and 35 and the minus bias graphicforms 25 and 47 obtained by the plus bias operation in the sixth stepST6 and in the seventh step ST7 are subjected to OR operation, to obtainan OR graphic form, and the design pattern 1 and the OR graphic form issubjected to exclusive OR operation, to obtain an XOR (exclusive OR)graphic form.

[Ninth Step ST9]

The XOR graphic form obtained by the graphic form operation in the stepsfrom the first step ST1 to the eighth step ST8 is subjected tomicro-recess/micro-projection removal operation. In this case, removalof a micro-recess is performed before removal of a micro-projection.

In an example shown in FIG. 12A, a pattern portion 1L has two adjacentedge portions having different space widths, wherein a correction amount“d” of each of the edge portions is positive. In this example, a microrecess 51 is formed at a corner, formed between the two adjacent edgeportions, of the pattern portion 1L. The micro-recess 51 is removed asfollows: namely, as shown in FIG. 12B, a square-shaped correctiongraphic form 53 having one side equivalent to the maximum value (forexample, d=+20 nm) of the plus correction amounts of the two adjacentedge portions is created at the corner of the pattern portion 1L, andthe correction graphic form 53 and the XOR graphic form 55 formed in theeighth step ST8 is subjected to OR operation. Here, if the originalcorrection amount “d” in the XOR graphic form 55 is not the maximumvalue, the correction graphic form 53 is protruded from the XOR graphicform 55. The protruded portion is removed as shown in FIG. 12C by thenext micro-projection correction operation.

In the creation of the correction graphic form 53 shown in FIG. 12B, thecorrection graphic form 53 may be subjected to movement operation so asto be accurately fitted in the micro-recess 51, as needed. In this case,the movement of the correction graphic form 53 may be moved inconsideration of the minimum grid.

In an example shown in FIG. 13A, a pattern portion 1L has two adjacentedge portions, wherein a correction amount “d” of one of the edgeportions is plus and a correction amount “d” of the other is minus. Inthis example, a micro-projection 57 is formed in an XOR graphic form 55shown in FIG. 13B. The micro-projection 57 is removed by preparing anabsolute value of the maximum value of the minus correction amount witha half of the maximum value of the plus correction amount “d”, andunder-sizing the XOR graphic form 55 by the larger value and thenover-sizing the XOR graphic form 55 by the same amount. Themicro-projection 57 is thus removed as shown in FIG. 13C.

The graphic form obtained by the above-described graphic form arithmeticoperation in the steps from the first step ST1 to the ninth step ST9 isused as an exposure pattern for photolithography. This exposure pattern,therefore, is that obtained by the rule-based OPC method to which thegraphic form arithmetic operation is applied.

According to the above-described exposure pattern forming method, thepattern portions 1L₁ to 1L_(z) having the target line widths L1 to Lzand the space portions 1S₁ to 1S_(z) having the target space widths S1to Sz are extracted by subjecting the design pattern to graphic formarithmetic operation. Accordingly, even for a pattern portion in whichthe space width of a space around the pattern portion is changed at apoint, the space can be accurately separated into two at the changedpoint, and each of the separated spaced portions can be accuratelyextracted as that having the corresponding one of the target widths S1to Sz. As a result, each of the pattern portions or each of the spaceportions can be accurately extracted as that having the correspondingone of the target line widths L1 to Lz or the corresponding one of thetarget space widths S1 to Sz irrespective of arrangement states of thepattern portions or the space portions. And, an edge portion of eachpattern, which is defined by each pattern portion and each spaceportion, can be accurately corrected by a correction amount allocatedthereto in Table 1.

Since a design pattern is corrected by subjecting each of the extractedportions to graphic form arithmetic operation based on each ofcorrection amounts allocated for each of the target line widths L1 to Lzand the target space widths S1 to Sz, an exposure pattern can beobtained by correcting the design pattern 1 only by graphic formarithmetic operation without use of any special measurement method andcorrection method. Accordingly, irrespective of the shape of the designpattern, for example, even if a pattern portion is tilted to anotherpattern portion, such a pattern portion can be corrected on the basis ofthe shape of the design pattern, to obtain an exposure pattern havingsmooth tilt lines.

As described above, it is possible to obtain an exposure pattern byaccurately correcting a design pattern, and in the case of forming atransfer pattern on a substrate by photolithography using such anexposure pattern, it is possible to certainly prevent occurrence of adefect such as short-circuit between transfer pattern portions anddisconnection thereof.

According to the above-described exposure pattern forming method and theexposure pattern, since both extraction of target pattern portions andtarget space portions and correction of the extracted portions are allperformed by graphic form arithmetic operation, it is possible toaccurately perform the extraction and correction irrespective ofarrangement states of the pattern portions and space portions.Accordingly, it is possible to obtain an exposure pattern by accuratelycorrecting a design pattern, and in the case of forming a transferpattern on a substrate by photolithography using such an exposurepattern, it is possible to certainly prevent occurrence of a defect suchas short-circuit between transfer pattern portions and disconnectionthereof.

1. An exposure pattern forming method of forming an exposure pattern bycorrecting each of pattern portions constituting a design pattern by acorrection amount, which amount is previously prepared so as tocorrespond to both a line width of said pattern portion and a spacewidth of a space portion adjacent to said pattern portion, characterizedby including the steps of: subjecting said design pattern to graphicform arithmetic operation, to extract each of said pattern portions foreach of target line widths, and to extract each of said space portionsfor each of target space widths; and subjecting each of said patternportion extracted for each of said target line widths and said spaceportion extracted for each of said target space widths to graphic formarithmetic operation based on the corresponding one of said correctionamounts, to thereby correct said pattern portion having each of saidtarget line widths for each of said target space widths.
 2. An exposurepattern forming method according to claim 1, further including the stepof: subjecting an edge of said design pattern to reduction correction byan amount equivalent to ½ of each of said target line widths and thensubjecting said edge of said design pattern to enlargement correction bythe same amount, to extract a pattern as a pattern portion having a linewidth larger than said target line width.
 3. An exposure pattern formingmethod according to claim 2, further including the step of: extracting adifference between two of said pattern portions obtained by saidextraction as a pattern portion having a target line width in a specificrange determined as a range from said target line width of one of saidtwo pattern portions to said target line width of the other.
 4. Anexposure pattern forming method according to claim 1, further includingthe steps of: subjecting an edge of said design pattern to enlargementcorrection by an amount equivalent to ½ of each of said target spacewidths and then subjecting said edge to reduction correction by the sameamount, to obtain a correction pattern; and subtracting said designpattern from said correcting pattern, to extract a graphic form as aspace portion having a space width being equal to or less than saidtarget space width.
 5. An exposure pattern forming method according toclaim 4, further including the step of: extracting a difference betweentwo of said space portions obtained by said extraction as a spaceportion having a target space width in a specific range determined as arange from said target space width of one of said two space portions tosaid target space width of the other.
 6. An exposure pattern obtained bycorrecting each of pattern portions constituting a design pattern by acorrection amount, which amount is previously prepared so as tocorrespond to both a line width of said pattern portion and a spacewidth of a space portion adjacent to said pattern portion, characterizedin that each of said pattern portions is corrected by subjecting saiddesign pattern to graphic form arithmetic operation, to extract each ofsaid pattern portions for each of target line widths, and to extracteach of said space portions for each of target space widths, andsubjecting each of said pattern portion extracted for each of saidtarget line widths and said space portion extracted for each of saidtarget space widths to graphic form arithmetic operation based on thecorresponding one of said correction amounts.